Mascara compositions have been used for many years to increase the thickness, length, and overall aesthetic appearance of human eyelashes and/or eyebrows. Consumers often expect particular properties from their mascara products such as adhesion to the lashes, lengthening/curling of the lashes, lack of smudging or flaking, thick lashes, and good separation of clumps of lashes. Particularly, the desire may be for long, luscious, full, soft, and separated lashes. Mascaras generally distribute a smooth and relatively thin (coating thickness) film over the eyelashes producing a satisfactory array of reasonably separated lashes that are darker and thicker than bare lashes, making the eyes more noticeably beautiful. In particular, at least some consumers desire a mascara to increase the volume of the eyelashes to make the eyelashes more noticeable. There are a variety of conventional mascaras available that claim to provide improved eyelash volume. Such mascaras are sometimes referred to as volumizing mascaras or volumizers. But in order to provide the increased volume, the volumizers may be formulated as a relatively thick (i.e., viscous) composition. In some instances, the applicator to apply the thicker volumizing mascara needs to be configured to apply thick compositions (e.g., larger core, increase spacing between bristles), which may not be as good for eyelash separation as applicators with a smaller core or closer bristle spacing.
Eyelash separation is also considered important for improving the appearance and noticability of eyelashes. Some mascara products are known to cause eyelash “clumping.” Clumping occurs when two or more eyelashes or eyelash portions stick to one another. Typically, the deposition of mascara has a coating that is 5-15 microns thick. But at least some volumizing mascaras tend to clump too many lashes together in a thick, less separated look which gives the perception of fewer lashes. While it is well understood that some lash clumping will naturally occur since lashes are arranged in both rows and columns above and below one's eye, complete separation of eyelashes is the “ideal” standard to be attained. A mascara product that is deemed by a user to separate well leaves fewer clumps of lashes than mascara that is deemed not to separate lashes well.
Producers of mascara products recognize that consumers desire a mascara product that provides improved volume and separation, and strive to design such a product. But there is currently no readily acceptable way to quantify eyelash clumping such that different mascara products (e.g., formulas, applicators, and the combinations of these) can be compared to one another in a standardized way. Rather, most manufacturers of mascara products rely on consumer opinions (e.g., test panelists) and/or other qualitative methods to determine whether a particular product provides sufficient eyelash separation. Qualitative methods may be sufficient for determining whether consumers perceive a particular product as providing desirable separation, but may not be suitable for product modeling/simulation and/or for supporting advertising claims directed to improved separation, especially when comparing a competitive product.
Accordingly, it would be desirable to provide a method for quantitatively determining the amount of eyelash clumping present when using a mascara product.